The 52-year-old Wesleyan and Yale-educated health care lawyer has scheduled an announcement for 6 p.m. in front of Blackstone Library, where sources say the Democrat will declare his candidacy in the 12th Senatorial District.

Having a Kennedy on the ballot is considered by some to be a coup for Democrats, who control both chambers of the General Assembly and the governor's office in this reliably liberal state.

"I think he's always been fueled by a sense of public service," said Democrat Ned Lamont, a former candidate for governor and U.S. Senate. "I think it's very deep in the genes."

Republicans are treating the Kennedy factor as the basis for a rallying cry.

"Despite the celebrity name, the last thing the voters of the 12th District need is another rubber-stamp vote for more of the same higher taxes and government spending that have held back Connecticut's economy and left more than half of our families living paycheck to paycheck," Jerry Labriola Jr., the state GOP chairman, said in a statement Monday.

Since 2002, the district has been represented by Edward Meyer, of Guilford, who is retiring at age 79 and has given his blessing to Kennedy to run. In 1967, Kennedy's uncle, Robert F. Kennedy, appointed Meyer as a federal prosecutor.

The district includes Branford, Durham, Guilford, Killingworth, Madison and North Branford.

By Kennedy standards, running for state Senate is hardly the lofty office that some Democratic stalwarts had envisioned for the married father of two.

Kennedy is said by multiple sources to have declined several attempts by high-profile Democrats to recruit him to run for the U.S. Senate seat of his father, Edward M. Kennedy, who died in 2009. He also wouldn't bite when John Kerry vacated his U.S. Senate seat in Massachusetts to become U.S. secretary of state.

Now that Kennedy's two children are in high school (Choate Rosemary Hall, the alma mater of President John F. Kennedy) and college, he is said to be more comfortable being in the public eye.

His wife, Katherine "Kiki" Kennedy, is from North Stamford and helped lead the successful fight against the construction of a liquefied natural gas terminal off the coast of Branford in Long Island Sound by Broadwater Energy.

Some Democrats privately view Ted Kennedy Jr. as heir apparent to U.S. Rep. Rosa DeLauro, D-Conn., if the 12-term incumbent from New Haven decides to retire.

Those familiar with the thinking of Kennedy, who hosted a fundraiser for Connecticut Democrats last year at his family's Hyannis Port compound on Cape Cod, say that the last thing the unassuming public servant-in waiting wants is a media circus.

"If I had to make a guess, he will go up to Hartford, roll up his sleeves and quietly take care of business," Lamont said.

Kennedy, a cancer survivor whose right leg was amputated when he was 12, co-founded the Marwood Group, a New York City-based health care advisory and financial services firm.